Vitamin D: Sunshine For My Spine
Vitamin D (calciferol), also known as the “sunshine vitamin”, is necessary for maintaining proper bones by regulating calcium and phosphorus levels within the body. When calcium levels are low, vitamin D acts as a hormone, signaling for more calcium to be absorbed and less to be excreted. In fact by normal definition, vitamin D is really a hormone and not a “true” vitamin because it can be acquired naturally with sun exposure. When sun exposure is limited however, vitamin D is considered a vitamin because it must be met through food sources.
Sun Exposure: Sunlight is responsible for providing most people with some of their vitamin D requirements. UV light converts compounds found in the skin to a form of vitamin D that is absorbed into the body and sent to the liver and kidneys to become activated or stored in fat tissue. When sunlight exposure is limited and in certain disease conditions, vitamin D must be taken in through the diet.
Dietary Sources: With
the exception of fatty fish, very few food sources contain vitamin D. In the
Source: USDA Nutrient Database for Standard Reference and Manufacturers
Do Older Adults Need More Than 600 IU/day?
Factors Affecting Vitamin D Status
· Clothing, window glass, clouds, shade, smog decrease UV rays
· Sunscreen with SPF of 8 or more prevents vitamin D synthesis.
latitudes and time of day and year. In
· Dark skin with high melanin content needs to be exposed to sun longer.
· Age (over 65) is associated with a fourfold decrease in vitamin D conversion compared to younger adults. Older people are also more apt to stay inside.
· Malabsorptive and kidney problems affect vitamin D status negatively.
Vitamin D Deficiency
· Children develop rickets
· Older people lose bone mineral content leading to osteomalacia and osteoporosis
Vitamin D Toxicity
· Not caused by sunlight or food intake. Mostly from supplements.
· Calcium deposits in soft tissue can occur with chronic intakes above the UL
How To Get Enough Vitamin D
· 10-15 minutes of sun exposure at least 2x/week on face, arms, back, and hands without sunscreen is adequate during summer months in Boston
· Older individuals and those who get little sun exposure need to include good food sources and a supplement in their diet
American Dietetic Association; Dietitians of
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Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes: Calcium, Phosphorus,
Magnesium, Vitamin D, and Fluoride.
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Vieth, R. (2004). Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults. Journal of Steroid Biochemistry and Molecular Biology, 89-90, 575-579.
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